Open Paleo

Tawa

Nesbitt et al., 2009 Ta-WAH

Named after Tawa, the Hopi sun god, reflecting the Hopi people's connection to the American Southwest where the fossil was discovered in New Mexico.

227.3–205.7 million years ago Norian, Late Triassic
Late Triassic stages

Tawa is a genus of possible basal theropod dinosaurs from the Late Triassic period. The fossil remains of Tawa hallae, the type and only species were found in the Hayden Quarry of Ghost Ranch, New Mexico, US. Its discovery alongside the relatives of Coelophysis and Herrerasaurus supports the hypothesis that the earliest dinosaurs arose in Gondwana during the early Late Triassic period in what is now South America, and radiated from there around the globe. The specific name honors Ruth Hall, founder of the Ghost Ranch Museum of Paleontology.

Under dispute

Tawa hallae is recovered within Morphoraptora in Herrerasauria by recent analyses (Novas and colleagues, 2021; Srivastava and colleagues, 2026) but as an early theropod, the sister of Neotheropoda (Nesbitt and colleagues, 2009) or of Chindesaurus (Marsh and colleagues, 2019); its mosaic anatomy drives the instability.

Diagnosis

  1. Deep recess on posterodorsal base of paroccipital process
  2. Sharp ridge extending dorsoventrally on middle of posterior face of basal tuber
  3. Incomplete ligamental sulcus on posterior side of femoral head with semicircular muscle scar on posterior face
  4. Small semicircular excavation on posterior margin of medial posterior condyle of proximal tibia
  5. Step on ventral surface of astragalus

Species

Tawa hallae Nesbitt et al., 2009

Type species

Named in honor of Ruth Hall, founder of the Ghost Ranch Museum of Paleontology.

Holotype
GR 241 , Ruth Hall Museum of Paleontology at Ghost Ranch
Material
Nearly complete associated but disarticulated skull and postcranial skeleton.
Horizon
lower Petrified Forest Member, Chinle Formation, Norian, Late Triassic , 227.3–205.7 million years ago
Locality
Hayden Quarry Site 2, Ghost Ranch, New Mexico, United States

References

  1. Nesbitt, S. J.; Smith, N. D.; Irmis, R. B.; Turner, A. H.; Downs, A.; Norell, M. A. (2009). A Complete Skeleton of a Late Triassic Saurischian and the Early Evolution of Dinosaurs. Science 326(5959): 1530-1533. American Association for the Advancement of Science (AAAS). doi:10.1126/science.1180350 nesbitt2009a
  2. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the body length and mass estimates, and the appearance features.

    paul2024a
  3. Srivastava, S.; Nesbitt, S. J. (2026). A new taxon of saurischian dinosaur from the Coelophysis Quarry of New Mexico, USA (Triassic: latest Norian or Rhaetian) highlights herrerasaurian diversity in the latest Triassic. Papers in Palaeontology 12(2). doi:10.1002/spp2.70069

    New Coelophysis Quarry taxon description recovering Tawa within Morphoraptora/Herrerasauria.

    srivastava2026a
  4. Novas, F. E.; Agnolín, F. L.; Ezcurra, M. D.; Müller, R. T.; Martinelli, A. G.; Langer, M. C. (2021). Review of the fossil record of early dinosaurs from South America, and its phylogenetic implications. Journal of South American Earth Sciences 110: 103341. doi:10.1016/j.jsames.2021.103341

    Recovered Tawa within Morphoraptora in Herrerasauria in their early dinosaur review

    novas2021a
  5. Marsh, A. D.; Parker, W. G.; Langer, M. C.; Nesbitt, S. J. (2019). Redescription of the holotype specimen of Chindesaurus bryansmalli Long and Murry, 1995 (Dinosauria, Theropoda), from Petrified Forest National Park, Arizona. Journal of Vertebrate Paleontology 39(3): e1645682. doi:10.1080/02724634.2019.1645682

    Redescribed Chindesaurus holotype, informing its relationship as sister taxon to Tawa

    marsh2019a
  6. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Treats Tawa as the sister of Chindesaurus at the base of Theropoda.

    jones2026c